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BackgroundThe SARS-CoV-2 pandemic urges for cheap, reliable, and rapid technologies for disinfection and decontamination. One frequently proposed method is UV-C irradiation. However, UV-C doses necessary to achieve inactivation of high-titer SARS-CoV-2 are poorly defined. MethodsUsing a box and two handheld systems designed to decontaminate objects and surfaces we evaluated the efficacy of 254 nm UV-C treatment to inactivate surface dried SARS-CoV-2. ResultsDrying for two hours did not have a major impact on the infectivity of SARS-CoV-2, indicating that exhaled virus in droplets or aerosols stays infectious on surfaces at least for a certain amount of time. Short exposure of high titer surface dried virus (3-5*10^6 IU/ml) with UV-C light (16 mJ/cm2) resulted in a total inactivation of SARS-CoV-2. Dose-dependency experiments revealed that 3.5 mJ/cm2 were still effective to achieve a > 6-log reduction in viral titers whereas 1.75 mJ/cm2 lowered infectivity only by one order of magnitude. ConclusionsOur results demonstrate that SARS-CoV-2 is rapidly inactivated by relatively low doses of UV-C irradiation. Furthermore, the data reveal that the relationship between UV-C dose and log-viral titer reduction of surface residing SARS-CoV-2 is non-linear. In the context of UV-C-based technologies used to disinfect surfaces, our findings emphasize the necessity to assure sufficient and complete exposure of all relevant areas by integrated UV-C doses of at least 3.5 mJ/cm2 at 254 nm. Altogether, UV-C treatment is an effective non-chemical possibility to decontaminate surfaces from high-titer infectious SARS-CoV-2.
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SummaryO_ST_ABSBackgroundC_ST_ABSPatients infected with SARS-CoV-2 exhibit a highly variable clinical course, varying from barely discernible signs of disease, to moderate flu-like symptoms and, occasionally, with life-threatening pneumonia and/or cytokine storm. The relationship between the nasopharyngeal virus load, IgA and IgG antibodies to both the S1-RBD-protein and the N-protein as well the neutralizing activity (NAbs) against SARS-CoV-2 in the blood of moderately afflicted COVID-19 patients has not been investigated longitudinally so far. MethodsSeveral new serological methods to examine these parameters were developed and validated for the longitudinal investigation in three patients of a family which underwent a mild course of COVID-19. FindingsWe observed that the virus load had almost completely disappeared after about four weeks, whereas serum antibodies showed a contrasting course. IgA levels to S1-RBD-protein and, to a lesser extent, to the N-protein, peaked about three weeks after clinical disease onset but declined soon thereafter. IgG levels rose continuously, reaching a plateau approximately six weeks after disease onset. NAbs in serum reached a peak about four weeks after disease onset but dropped to a lower level about six weeks later. InterpretationOur data establishes associations of virus neutralization and a serological immune response foremost against Sars-CoV-2 S1-RDB-protein in a longitudinal manner.
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The majority of infections with SARS-CoV-2 are asymptomatic or mild without the necessity of hospitalization. It is of importance to reveal if these patients develop an antibody response against SARS-CoV-2 and to define which antibodies confer virus neutralization. We conducted a comprehensive serological survey of 49 patients with a mild course of disease and quantified neutralizing antibody responses against a clinical SARS-CoV-2 isolate employing human cells as targets. Four patients (8%), even though symptomatic, did not develop antibodies against SARS-CoV-2 and two other patients (4%) were only positive in one of the six serological assays employed. For the remainder, antibody response against the S-protein correlated with serum neutralization whereas antibodies against the nucleocapsid were poor predictors of virus neutralization. Regarding neutralization, only six patients (12%) could be classified as highly neutralizers. Furthermore, sera from several individuals with fairly high antibody levels had only poor neutralizing activity. In addition, employing a novel serological Western blot system to characterize antibody responses against seasonal coronaviruses, we found that antibodies against the seasonal coronavirus 229E might contribute to SARS-CoV-2 neutralization. Altogether, we show that there is a wide breadth of antibody responses against SARS-CoV-2 in patients that differentially correlate with virus neutralization. This highlights the difficulty to define reliable surrogate markers for immunity against SARS-CoV-2.
